Abstract: An engine was destroyed during long testing of 300 h because of the fracture of the high pressure turbine disk whose material was FGH4097 powder superalloy, the fracture of the disk was analyzed through the macro and micro observation and EDS analysis, and a simulation test was performed on the basis of the analysis results of failure causes. The results show that the fracture of the the turbine disk was fatigue fracture. The causes for the fatigue fracture were the inclusion existing in cooling aperture of the disc and prior particle boundary(PPB) around the inclusion. The inclusion was main arc-welding slag, and the PPB was a concomitant resulted from the reaction of the welding slag and the alloy.